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This is because add_dt_node() -> dlpar_attach_node() attaches only the
parent node returned from configure-connector, ignoring any children. This
should be corrected for the general case, but fixing that won't help with
the stale OF node references, which is the more urgent problem.

I don't follow. If the code path you mention is truly broken in the way you say
then DLPAR operations involving nodes with child nodes should also be
broken.

Hmm I don't know of any kernel-based DLPAR workflow that attaches
sub-trees i.e. parent + children. Processor addition attaches CPU nodes
and possibly cache nodes, but they have sibling relationships. If you're
thinking of I/O adapters, the DT updates are (still!) driven from user
space. As undesirable as that is, that use case actually works correctly
AFAIK.

What happens for the platfac LPM scenario is that
dlpar_configure_connector() returns the node pointer for the root
ibm,platform-facilities node, with children attached. That node pointer
is passed from add_dt_node() -> dlpar_attach_node() -> of_attach_node()
-> __of_attach_node(), where its child and sibling fields are
overwritten in the process of attaching it to the tree.

Well it worked back in 2013 when I got all the in kernel device tree update
stuff working. Looks like I missed this one which now explains one area where
platform-facilities update originally went to shit.

commit 6162dbe49a451f96431a23b4821f05e3bd925bc1
Author: Grant Likely [off-list ref]
Date:   Wed Jul 16 08:48:46 2014 -0600

    of: Make sure attached nodes don't carry along extra children

    The child pointer does not get cleared when attaching new nodes which
    could cause the tree to be inconsistent. Clear the child pointer in
    __of_attach_node() to be absolutely sure that the structure remains in a
    consistent layout.

    Signed-off-by: Grant Likely [off-list ref]

diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
index c875787fa394..b96d83100987 100644
--- a/drivers/of/dynamic.c
+++ b/drivers/of/dynamic.c

@@ -98,6 +98,7 @@ int of_property_notify(int action, struct device_node *np,

 void __of_attach_node(struct device_node *np)
 {
+       np->child = NULL;
        np->sibling = np->parent->child;
        np->allnext = np->parent->allnext;
        np->parent->allnext = np;

Not sure what the reasoning was here since this prevents attaching a node that
is a sub tree. Either need to revert that, rewrite dlpar_attach_node to iterate
over the sub-tree, or probably best rewrite dlpar_configure_connector to use a
of_changeset instead.